Green tea is an herbal beverage that stands out as a favorite drink in many Asian countries and has recently taken a spotlight all over the world as its several efficacies in the human body have proven. Green tea is known to contain a variety of ingredients, such as polyphenols, protein amino acids, vitamins, minerals, and so forth. Among these ingredients of green tea, polyphenols, particularly epigallocatechin gallate (EGCG), known to have strong anti-oxidant and anti-cancer effects have been the subject of a number of studies.
However, there is a growing interest in theanine, an amino acid specifically abundant in Camellia sinensis, since theanine has proved as an ingredient that is a major determinant in providing the savor and efficacy of green tea. Theanine is biosynthetically produced through an enzyme reaction of glutamine and ethylamine in the root of Camellia sinensis, transferred to the leaves and concentrated. Theanine in the leaves is partly converted to polyphenols by the sun light but mostly exists in the form of free amino acids, the amount of which is known to be 1 to 2% of the total dry weight of the leaves, taking over 50% of the total amino acids. The studies on the efficacy of theanine have been made focusing on the benefits of theanine related to the nerve system, such as it promotes Alpha wave generation in the drain, a sign of induced relaxation, reduces physical and mental stress, and protects nerve cells. Recently, it has been reported that theanine has efficacy in skin moisturization and promotion of collagen biosynthesis through activation of prolidase, but the studies on the efficacy of theanine in the skin are not entirely satisfactory. Like this, many studies are being made on the theanine derivatives as well as theanine, such as the theanine derivative with enhanced stability (U.S. Patent Application Pub. No. 2008/0009505) as the benefits of theanine in the skin have been demonstrated.
In this context, the inventors of the present invention have been studying on theanine and its derivatives and growing more interested in the theanine derivatives bound to sugar. There are a variety of methods of introducing a sugar into a theanine derivative, most of which have some problems, such as necessity of involving complicated steps of introducing and removing a protective group. But, the use of the Amadori rearrangement reaction enables introduction of a sugar into a theanine derivative without carrying out the complicated steps, such as of adding a protective group. However, the progress of the Amadori rearrangement reaction leads to conversion of a desired product into a different substance and increased yield of by-products, consequently with the difficulty in obtaining a desired product at high yield.
For the reason, the methods use more sugars than needed in the actual reaction and need to isolate a desired product using an ion-exchange resin after the reaction, which is uneconomical and unsuitable for large-scale production. Furthermore, the desired product in many cases possibly has deterioration in color by the effect of by-products. Accordingly, there is a need for improving those problems.
On the other hand, different kinds of bacteria form a specific colony in the skin and play a role as a primary barrier protecting against external microorganisms entering the human body. It is however known that an abnormal proliferation of bacteria harmful to the skin causes skin problems, where the representative one of such bacteria is Propionibacterium acnes (P. acnes) known to cause acnes in the skin. There have been made attempts to find out a substance that has a selective anti-bacterial effect on Propionibacterium acnes without affecting other bacteria existing in the skin but insignificantly harmful to the skin. Theanine is known to have an anti-bacterial effect, which is insignificant. Thus, there is a need for improved effects of theanine for the sake of the practical use of theanine.